Remote control apparatus



March 4, 1952 A. P. DAVIS ET AL 2,588,213

REMOTE CONTRQL APPARATUS Filed Dec. 12, 1936 5 Sheets-Sheet 1 ENWS AMarch 4, 1952 A. P. DAVIS ET AL REMOTE CONTROL APPARATUS 5 Shee ts-Sheet`2 Filed DSC. 12, 1936 VEN R v March 4, A. P, DAVls ETAL 2,588,213

REMOTE CONTROL APPARATUS 3 Sheets-Sheet 3 Filed Dec. l2, 1936 PatentedMar. 4, 1952 UNITED STATS @PATENT OFF-ICE REMOTE CONTROL APPARATUSArthur P. Davis, New York, :and George Agins,

Brooklyn, N. Y., assignors to Arma Corporation,

a corporation of NewYork Application December 12, 1936, Serial No.115,488

(Cl. S18-31) 23 Claims. l

This invention relates to control systems and has particular referenceto follow-up control systems in which a local or remote controlledelement may be instantaneously driven at a rate of speed and through adistance or angle corresponding to the rate and extent of movement of acontrolling element.

The follow-up systems in general use, especially those adapted for heavyduty Work, are complicated and expensive and where a relatively highdegree of accuracy is required, the sensitivity necessary to gain suchaccuracy is accompanied by objectionable hunting oi the controlledelement. Such systems usually employ sensitive but delicate electronicvalve arrangements which are likely to get out of order. All of theadvantages of electronic follow-up control systems are realized in thesystem of the present invention while eliminating their disadvantages tothe end that a rugged, simple, inexpensive and nonhunting system isprovided, which is readily adaptable to various industrial uses where itis desired to accurately and rapidly position one or more light or heavycontrolled elements in accordance with the movements of a local orremote controlling element.

The control system of the present invention includes a reversingswitching mechanism, one member of which is driven by a relatively lowtorque pilot motor controlled by the controlling element, and the othermember of which is operatively connected to a relatively high torquedriving motor controlled by the switching mechanism and driving thecontrolled element, this driving motor being so connected to theswitching mechanism that the corresponding switch member is driven inthe same direction that the other switch member is driven by the pilotmotor. As long as the two switch members of the switching mechanismremain in engagement, the controlled element will be driven at the samerate and will follow the controlling element, but if there is a changein relative speeds the reversing switching mechanism will first breakand then instantly restore the control circuit, usually by engaging thereversing contacts, in' accordance with the rate or direction ofmovement of the pilot motor, thus maintaining the controlled element inpositional agreement with the controlling element.

The pilot motor may be either of the alternating or direct currentreversible type, whose acceleration is less than that of the drivingmotor in order to prevent dragging by the pilot motor, and the reversingof the pilot motor is controlled in accordance with any reversing orspeed change a movement of the controlling element by suitable switchingmeans, such as rotary induction apparatus for actuating high and lowspeed switches for appropriately controlling the energization oi thefield coils of the pilot motor. Damping is efiected by simple means,located in the connections between the pilot and driving motors, causingthe restoring torque to be applied so as to lead in phase by more thanand less than 270c the displacement of the oscillating member, so thatthere is no hunting.

It will be seen that a very sensitive and accurate following movementwithout hunting is obtained by the simple and durable electro-mechanicalcontrol system of the present invention, Without the use of complicatedelectrical circuits. electronic valves, or involved mechanism. Becausemechanical as well as electrical coupling is employed between thecontrolling and the controlled elements, they remain in synchronism sothat no low speed control is required for the power follow-up. Thesystem is equally adaptable t0 alternating and direct current servicefor reproducing the movement of any controlling element such as a'handwheel, lever, telescope and the like, or for adjusting a remotecontrolldelement in accordance with impulses developed by .photoelectricdevices, thermostats, valves, oats, .air oriiuid iiow meters andapparatus, and the like.

For a more complete understanding of the invention, reference may be hadto the accompanying drawings, in which:

Figure 1 is a schematic diagram of the control system of this inventionas adapted to alternating current service;

Fig. 2 illustrates schematically the adaptation thereof to the controlof a direct current or series alternating current motor;

Fig. 3 is a theoretical graphic analysis of the damped system;

Fig. 4 is a face view of a preferred embodiment of the reversingswitching mechanism;

Fig. 5 is an axial section therethrough as seen along the line 5 5 ofFig. l4;

Fig. 6 is a fragmentary section through the dash-pot damping device asseen along the line E-S of Fig. 4;

Figs. 7a, 7b, 7c and '7d arevector diagrams illustrating the phaserelationship of the current through a three-phase driving power motor;and

Fig. 8 is a diagrammatic illustration of an adaptation of the controlsystem employing a mechanical differential.

Merely by way of illustrating one adaptation of the control system ofthis invention, the contors of receivers 25 and 25. 'low speedcommutator switch I8 is provided with 'two opposed short segments 29 and3|) suitably ataeis trolled element I is illustrated as a gun mountwhile the controlling element is illustrated as a telescope, bothelements being adjustable in train. It is of course understood that theinvention is applicable to innumerable uses, some of which have beenmentioned. In Fig. 1 the gun mount Ill is driven by a suitable powerlnotor, such as the three-phase motor I2 connected thereto by suitablegearing I4.

Two phases, |52 and |53 of the three-phase stator winding of drivingmotor |2 are energized by a reversing switch generally designated I5,which is actuated by a pilot motor oi a suitable alternating or directcurrent reversible type, such as that illustrated in this instance asreversible by energizing either of its two iield coils. For normaloperating conditions, the acceleration of the driving motor I2 should begreater than that of the pilot motor |'I in order to prevent dragging bythe pilot motor. The

lpilot motor is controlled by commutator switches I3 and |9 ofrespective low and high speed contact follow-up systems.

The remote controlling element, such as the vtelescope II, is connectedby suitable gearing 20, 2| and '22 to respective low speed and highspeed transmitters 23 and 24, which are preierably of theself-synchronous induction type.

Transmitters 23 and 24 are respectively connected to receivers 25 and25, also of the selfsynchronous induction type, the rotors o which 'areaccordingly maintained in positional agreekment with the rotors of thetransmitters 23 and 24. The low and high speed commutator switches |8and I9 are respectively controlled by the -low and high speed receivers25 and 25, by suit- 'able connections between corresponding stators androtors thereof, such as by concentric shafts 21 and 28. Gears |24 and|25 are journalled at'the ends of the shafts of the respective sta- 'Ihegear |24 of insulated from two opposed long segments 3| and 32.

The gear |25 of high speed commutator switch '|9 is similarly providedwith two opposed short *segments 33 and 34, which are insulated from twoopposed long segments 35 and 35. Secured "to low speed rotor shaft 2l isa slip ring 3l 'which is electrically connected through trolley or brush38 to one of the outer segments 29, 35,

13| orY 32, depending upon its angular position, "while commutator ring3l is electrically connected by trolley or brush 39 to one side of the'supply line I3.

Similarly, commutator ring 4|) of high speed A`commutator switch I9 iselectrically connected through double contact trolley 4| to one or twoof the outer segments 33, 34, 35 or 36, while the commutator ring 45 iselectrically connected to lsegment 29 of low speedv commutator switch I8by brush 42. The two contacts of the double trolley 4I are so spaced inrelation to the short "segments `33 and 34 of high speed commutator'switch' I9 as to make the eiiective gap on either side of its centralposition very short.

Long segments 32 and 35 of respective low yand high speed commutatorswitches I8 and I9 vare electrically connected to one field coil 43 oi@pilot motor Il while segments 3| and 36 are electrically connected tothe reversing eld coil 4,4,4 of pilot motor Il. Both field coils 53 and44 ,are connected to one side of the supply line I3.

'Y Armature 45 of pilot motor I1 is electrically through resistance 46while its other terminal is connected to the common terminal of heldcoils 43 and 134. The shaft 5l of pilot motor il, through suitablegearing 48 and 55, drives the gear |25 of high speed commutator switchI9 in the same direction and through the same angle as previously madeby the rotor shaft 23 and, through the gearing "49 and 5i, drives thegear |24 of low speed commutator switch I8 in the same direction andthrough the same angle as previously made by the rotor shaft 2l. Thestructure of such cominutator switches is well known and need not beillustrated or described in detail. Condensers 5| with protectiveresistances 62 are connected across contacts for suppressing arcing.

When the controlled element, or gun l5, is in positional agreement withthe controlling element, or telescope II, the position of trolleys 38and 4| is such that neither eld winding 43 nor 45 of pilot motor il isenergized and the Ypilot motor is stationary. II trolleys 38 and 5|engage respective segments 32 or 35, the field coil 43 is energized tocause pilot motor Il to rotate in one direction, whereas if trolleys 33and 3| engage respective engagements 3| or 35, the other eld coil i4 isenergized to cause pilot motor to rotate in the reverse direction. Rotation of the pilot motor in this way causes actuation of the reversingswitch Ic to which the pilot motor is connected by shaft 51 through asuitable mechanical iilter 52 to gears 53, 55 and 55.

The mechanical ilter 52 is employed to absorb irregularities in theinput of pilot motor ll and in one form may consist of a collar 5lsecured to the shaft 5l and having connected thereto one end of aplurality of equally spaced radial helical springs 58, the opposite endsof which are connected to posts 59 iiXed to a flange 59 of one of thegears 53, which is journalled on shaft 5l, and meshes with the other ofgears 53. Weights in the form of rings 53 and E13 are adjustably clampedto the flange 55 by means of screws 55, so that a predetermined increasein acceleration will cause a relative slip between the rings 53-55 andthe ang'e 5|), thus providing auxiliary damping. Other suitablemechanical filters may be employed with equal facility.

As is illustrated in Figs. 4 and 5, gear 55 is secured to a hub 5lhaving diametrically opposite radial arms 58 and 55l and journalled onthe sleeve 75, which is in turn journalled on shaft Tl of the drivingmotor l2. Arm 69 is pivotally connected by lateral pin i2 tc the movablevalve block I3 of a dash-pot generally designated 55 and illustrated inpartial section in Fig. 6. The two opposed pistons i4 are fixed to theopposite vendsof a relatively flxed bracket l5 and iit closely withintwo corresponding cylinders 'i5 carried by movable valve block T3. Theblock 'E3 is flexibly suspended between the inner ends of twon'metallicbellows 'il secured at their opposite ends to bracket lt and forming atight,

i arm 8| and two colinear arms 82 positioned at right angles to the arms8E] and 8| and which stops 83 for the arm 68.

warms' 69 and `98 respectively overlie asis shown in Fig. 4. Arm 8| isfitted with opposite limit These stops `B3 each comprise a stud 84slidably mounted within a housing 85 on arm 8| and urged outwardly by acoil spring 89, the tension of which is adjustable by means of nuts 89.The hanged heads 87 of studs S4 engage opposite sides of the reduced endof arm 88, the springs 88 serving to hold arm 68 in a central positionand the face of housing 85 serving as a limit stop for each direction ofmovement of arm 88. Sleeve 19 is accordingly rotated by gear 55 througharm 99 yand either dash-pot 59, depending upon the direction ofrotation.

Arms 82 of sleeve 'I9 carry opposite contacts 89 and 99, which have alarge contact surface and which are insulated from the arms B2, as isillustrated in Fig. 5. As sleeve 19 rotates in either direction, thecorresponding contacts 89 and 99 move through a narrow gap or dead spaceand contact either contacts 9| and 92 in one direction or 93 and 99 inthe other direction, these contacts also having correspondingly largecontact surfaces. Contacts 9|, 92, 93 and 94 are each carried by anarcuate support 95 in turn supported by rollers 96 on disc 91 secured toshaft 1| of the power driving motor I2. Collector rings 98 on the rearface of disc 91 serve to make electrical connections with proper brushes93.

At each contact support 95, a post 99 secured to disc 91 projectsthrough a hole |92 in the contact support and is connected to one end ofa coil spring I9 i, the other end of which is secured to a post |99 onsupport 95. This arrangement is illustrated in Fig. 4 as applied tocontact 93 and with it each contact is maintained with its Contactsurface substantially parallel to the surface of cooperating contact 99or 99 during rotation of disc 91, the tension of spring I9| resilientlyholding contact 93 in position. The contacts 9| to 94 are so shaped andarranged about the center of rotation as to be insensitive tocentrifugal forces of rotation and yet enough movement is provided toassure positive contact of both upper and lower contacts 89 and 99 ofarm 82 with corresponding contacts 9|, 92, 93 and 94. For alternatingcurrent operation it has been found preferable to position one contactslightly in advance of the other, so that the pair of contacts 9| and 99are displaced slightly unsymmetrically with respect to the correspondingopposite contacts, as illustrated in an exaggerated manner in Fig. l.For direct current operation, an unsymmetrical arrangement of thecontacts, as indicated in Fig. 2, is also desirable. If two equalresistors |23 are added as indicated, contact 9| is set closer to 99than its cooperating contact 92 is to 99, and contact 99 is set closerto 99 than its cooperating contact 93 is to 89, results similar to thoseon A. C. operation are obtained. The contact rst made causes one of theresistors |23 to be placed in series with the armature I3 and the otherresistor in parallel with the iirst resistor and armature, thus reducingthe torque on the first step.

Suitable electrical connections are made through slip rings 9B andbrushes 98' between the contacts 89 to 94, the power source |93 and thedriving motor I2, so that the latter is energized to rotate in onedirection when one set of contacts is engaged, for example, 89 and 9|,99 and 92, and to rotate in the reverse direction when the other set ofcontacts is engaged, for example 89 and 93, 99 and 94. Disc 91 may bemounted directly on the shaft 'II of driving power motor I2, asindicated in Fig. 5, or may be geared to the shaft 1I of driving motorI2 by gear |95 `meshing with the toothed periphery of disc 91, asindicated in Figs. 1 and 2. With either of these arrangements, disc 91with its attached contacts 29|, 92, 93, 94 is correspondingly rotatedinto positional agreement with arms 82 so that a follow-up movement iseffected.

Three-phase connections to driving motor I2 are illustrated in Fig. 1although it is to be understood that any polyphase motor may be employedwith equal facility. In the arrangement shown, contacts 9| and 94 areconnected to one phase |933 of the three-phase supply I 93, contacts 92and 93 are connected to another phase |932 of supply |93, contact 89 isconnected to one phase I 52 of three-phase stator l5 of driving motorI2, contact 99 with another phase |53 of stator winding I5, while theremaining phase |51 of stator winding i9 is directly connected to thethird phase |931 of supply |03.

Resistances |99 are connected in Y relation with the windings of thethree-phase rotor |3 of driving power motor I2 for the purpose oflimiting the starting current and increasing the starting torque.Condensers |99 are connected across the several contacts 39 to 94 forsupressing arcing, while condenser |91 is connected across the windings|52 and |53 of stator I5, as indicated, for the purpose of carryingsufficient split phase current to drive rotor I3' and disc 91 when onlyone set of contacts of reversing switch I6 is engaged. If condenser I 91were omitted, two phases of driving motor I2 might be energizedcontinuously, causing the motor to overheat.

Fig. 2 illustrates the connections for a direct current or a seriesalternating current driving motor I2', the commutator and pilot motorconnections being omitted in Fig. 2 in the interest of simplicity, butit will be understood that they are identical or equivalent to thoseillustrated in Fig. l. In this arrangement, electrical connections aremade between contact 89 and one terminal |98 of the armature I3 ofdriving motor l2', while contact 99 is connected to the other terminal|99. Contacts 92 and 93 are connected together and in series with theeld coil I|9 of motor I2 and a resistance III to one side of the supplyline |3. Contacts 9| and 99 are connected together and to the other sideof the supply line I3. Condensers II3 are provided across the contactsfor the purpose of arc suppression.

In operation, with the controlling element il in positional agreementwith the controlled element I9, the system is in its normal deenergizedcondition as illustrated in Figs. l and 2. Rotation of the controllingelement II, such as by hand, effects a corresponding multiplied rotationof the rotors of respective low speed and high speed transmitters 23 and24, which results in an equal and substantially simultaneous movement ofthe rotors of respective low speed and high speed receiver motors 25 and29. Double trolley 4I of high speed commutator switch I9 is accordinglydisplaced to engage either segment 35 or 38, depending upon thedirection of rotation of the controlling element II. This effectsenergization of the appropriate eld coil i3 or 94 of pilot motor I1,causing the latter to rotate shaft 't1 in the appropriate direction, andalso connected gears 68 and 99 which eiect rotation of the correspondinggears |25 and |29 until the corresponding high and low speed commutatorswitches I9 and I8 'are again in their open positions. f

Y .The movement of pilot motor Il is transmitted through shaft 41, gears53 and 5, to' gear 55 oi reversing switch |5. trolling element II is ina direction such as to cause gear 55 to rotate counterclockwise, arm 69of gear 55 effects movement oi arms 8! and S2 through the dash-potmechanism 55 so that contacts 90 and 92 and 8S and 9i engage, therebyenergizing driving motor l2 to rotate in a counter-clockwise directionand move controlled element I through the corresponding angle ofmovement initiated by the controlling element II, so that element I isplaced in positional agreement with elment I I. Disc Si is also drivenIin a counter-clockwise direction so that posi- Vopposite direction, sothat gear 55 rotates clockwise, then arm 59 through dash-pot 55correspondingly rotates arms 80 and 82 so that contacts 95 and 94, and89 and 95 engage, thus energizing motor I2 for rotation in a clockwisedirection.

In the event that the controlled element I for some reason is unable tofollow rapid movements of the controlling element I I so that theelements are displaced more than a permissible amount, trolley 38 of lowspeed commutator switch I3 will have been advanced to a point 'where itno longer makes contact with segment 29 and accordingly disconnectsdouble trolley di or" high speed commutator switch I9 from the supplyline I3, so that the high speed commutator switch I9 becomes inoperativeand control is assumed by low speed commutator switch I8. When angularcorrespondence between elements il! and II is again approximated,trolley 38 is again moved into engagement with segment 29, so as torestore control to high speed commutator switch I9.

Where a three-phase driving motor I2 is employed as in the arrangementof Fig. l, with counter-clockwise rotation so that contacts Sty and 9|are engaged, one phase |033 of the supply |03 is connected to thecorresponding winding |52 of stator I5, As contacts 95 and 92 are alsoengaged under these conditions, another phase |032 of supply |03 isconnected to the corresponding stator winding |53. lnasmuch as therevmaining stator winding |51 is permanently connected to the thirdp-hase i531 of the supply |53, all three phases of stator winding i5 arethus energized to cause rotation of the driving motor I2 in thecorresponding direction, say clockwise.

Fig. 7a is a vectorial representation of the phase energization instator winding i5 corresponding to the phases of supply just described.

With clockwise rotation of disc 9i, contacts 89 and 9.3 are engaged toconnect phase |632. of supply |93 with the corresponding winding |52 ofstator I5, while the corresponding engagement of contacts 95 and 9econnects phase |533 oi supply |53 with the corresponding winding |53 ofstator I5, thus reversing the phase in two windings of stator I5 tocause reversal of rotation of driving motor I2 in a counter-clockwisedirection. The vector diagram of Fig. 7c illustrates this phaserelationship.

At the start of rotation in a counter-clockwise direction, when only oneset of contacts are engaged, say contacts 89 and 9|, correspondingwindings |51 and |52 of stator i5 are directly energized, but not thethird winding |53. How- If the rotation oi the conas before in aclockwise direction. This phase relation is illustrated diagrammaticallyby the vector diagram of Fig. 7b. Similarly, in the opposite direction,split phase energization of winding |52 of stator I5 causes rotation ina counter-clockwise direction, the phase relationship being illustratedin Fig. 7d.

Where a direct current or series alternating current driving motor l2 isemployed, as illustrated in Fig. 2, the direction of rotation of thedriving motor I2 is reversed by reversing the connections to thearmature thereof. Thus, when contacts 89 and 93, 90 and 96 are inengagement, armature terminal |03 is connected to one side of the supplyI3, whereas when contacts 89 and 9|, 99 and 92 are in engagement,armature terminal |03 is connected to the other side of the supply I3.

Accordingly, the reversal of reversing switch IS changes the directionof rotation of the driving motor I2 or I2 and thus of the controlledelement Il), in both of the arrangements illustrated in Figs. 1 and 2.Follow-up movement is obtained so that the controlled element i5 ismaintained in positional agreement with the controlling element I I atall times.

In the event of an undamped vibration, the restoring force is dependenton the displacement and is opposite in sign. The phase of the velocityis 90 ahead oi that or" the displacement and if the oscillation isdamped, there is an additional force dependent on the velocity andopposite in phase. This additional force leads that due to displacementby 90, so that the resultant force leads that due to displacement bysome amount less than 90. Although the hunting oscillation of thefollow-up system is not sinusoidal and the restoring force does not varycontinuously with the displacement, nevertheless the problem may beanalyzed in the same way, that is to say, the oscillation will be dampedif the torque leads that'due to displacement by some amount less valuesof displacement, velocity and torque of the undamped system are plottedas ordinates against time as the abscissa. In Fig. 3, S designatesdisplacement and is representedY as a nonsinusoidal curve, T designatesthe restoring torque as a rectangular discontinuous curve, and Vdesignates the velocity as a flat-topped curve. For the undampedoscillation shown, the torque T leads displacement S by in phase. Thus,if a torque is applied which is less than 90 out of phase with thetorque T and leading, as is indicated by the dotted curve T', dampingwill result.

This form of damping is realized in the present apparatus and may beexplained conveniently if one cycle of oscillation is considered at thebeginning of an attempted hunt. Referring to Figs. 4, 5 and 6, andassuming that gear 55 rctates in a counter-clockwise direction, contactarm 8|!v is moved through dash-pot connecting pin 'F2 until contacts 90and 92, 89 and 9| engage. Disc 91, being caused to rotate in acounterclockwise direction by the responsive energization of drivingmotor I2, will move the contacts away from arm 82 so that arm 82 thenstarts its return oscillation. Because of the braking yaction of thedash-pot mechanism 55. arm 82 will lag behind gear 55, so that uponreversal, i. e., in clockwise direction of rotation, arm 82 will leadgear 55. Contacts dal and 94, 89 and 93 are accordingly engaged soonerthan would be the case if the dash-pot mechanism 53 were not employed,and driving motor i2 is also energized to rotate in the reverse orclockwise direction at an earlier time, so that the restoring torque isapplied earlier, that is, the torque is applied ahead of the clockwisereturn motion of arm 32 and also of pilot motor I I and controllingelement I I. This lead takes place for each subsequent reversal ofmotion, so that the resultant restoring torque leads the displacementtorque by less than 90, which is the proper condition to be establishedfor ei- :fective damping, with the result that hunting is prevented.

A further adaptation ci the control system of this invention isillustrated diagrammatically in Fig. 8, in which the pilot motor I'! iscontrolled as before but its shaft l? drives one input of mechanical.differential H5, while gear H5, the other input of the differentialII5, is driven by gear II'l on the shaft 'H of driving power motor I2.The output gear Ile of the differential II5, through gears IHS, causestoothed sector IIl to rotate about its pivot |23 through a slight anglein either direction, depending upon the difference between the angularinputs o'f shafts 4l and ll. Sector I I9 is provided with an eritensionIZi having a fork I22 at its extremity, which engages pin 'f2 ofdash-pot mechanism 555, so as to cause a corresponding movement of armE12 carrying contacts 89 and 9i! and pivoted at Iza on tbe reversingswitch base l5 which is providedY with the stationary contacts 9! toinclusive. electricallv connected as before. Reversal of switch I6accordingly reverses the direction of rotation of driving motor I2 inthe manner previously described.

With this simple electro-mechanical arrangement the controlled elementIll accurately and rapidly follows the controlling element I I. Also,with this arrangement, as with the arrangement of Figs. l and 2. no lowspeed control is required on the power follow-up because of themechanical coupling between the controlling and controlled elements.which prevents them from getting out of synchronism.

It will be observed that in the event of power failure, the control ofthe center contacts 89, 99. by the controlling element. such as ahan'iwheel. I 2l' connected to gear 50.- by pinion ld thro-uch normallydisengaged clutch it@ (Fig. l), enables continued operation withoutreouiring shifting of parts, closing of auxiliary switches. and thelike. This advantage is due to the electromechanical coupling affordedby the mechanism of this invention. The only evidence of such powerfailure is that greater torque is required of the operator in moving thecontrolling handwheel or element.

While certain preferred embodiments cf the invention have beenillustrated and described herein, it is to be understood that theinvention is not limited thereby but is susceptible oi changes in formand detail within its scope.

We claim:

1. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a driving motor for said controlledelement, a source of power, a switch having two sets of cooperatingmovable contacts directly controlling said motor, connections betweenone set of said contacts and said powersource for controlling theinitial operation of said motor, connections between the other set ofsaid contacts and said power source for controlling the subsequentoperation of said motor, driving connections between one Contact of eachset of contacts and said motor, operative connections between saidcontrolling element and the other contact of each set of contacts, anddamping means for regulating the relative movement between saidcontacts.

2. In a system including a controlling element and a controlled elementgoverned thereby, the. combination of a driving motor for saidcontrclled element, a source of power, a switch having two sets ofcooperating movable contacts directly controlling said motor,connections between one set of said contacts and said power source forcontrolling the initial operation of said motor, connections between theother set of said contacts and said power source for controlling thesubsequent operation of said motor, driving connections between onecontact of. each set of contacts and said motor, operative connectionsbetween said controlling element and the other contact of each set ofcontacts, and damping means in at least one of said connections.

3. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a driving motor for said controlledelement, a switch having two sets of cooperating movable contactsdirectly controlling said motor, driving connections between one contactof each set of contacts and said motor, ope"ative connections betweensaid controlling eement and the other contact of each set of contacts,said sets of contacts being successively engageable to apply successivepower impulses to said motor, and damping means in said lastnamedconnections.

4. In a system including a controlling element and a controlled elementgoverned thereby, the cfmbination of a driving motor for said controledelement, a switch having two sets of cooperating movable contactsdirectly controlling said motor, driving connections between one contactof each set of contacts and said motor, a pilot motor controlled by saidcontrolling element, and driving connections including damping meansbetween said pilot motor and the other contact of each set of contacts,said sets of contarts being successively engageable to apply successivenower impulses to said motor.

5. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a reversible driving motor for saidcontrolled element, a reversing switch having two sets of cooperatingmovable contacts directly controlling said motor, driving connectionsbetween one set of contacts and said motor, a reversible pilot motor,means actuated by said controlling element for controlling said pilotmotor in accordance with the direction of movement of the controllingelement, and driving connections including damping means between saidpilot motor and the other set of contacts.

6. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a reversible driving motor for saidcontrolled element, a reversing switch having two sets of cooperatingmovable contacts directly controlling said motor, driving connectionsbetween one set of contacts and said motor, a pilot motor controlled bysaid controlling element, driving connections between said pilot motorand said other set of contacts, a iirst switch between said pilot motorand said controlling element and actuated by the latter, a second switchbetween said pilot motor and said controlling element and actuated bythe latter, said second switch being responsive to a predetermineddisplacement between said elements for appropriating control of saidpilot motor from said first switch, and damping means in at least' oneof said connections.

7. In a system including a -controlling element and a controlled elementgoverned thereby, the combination of a reversible driving motor for saidcontrolled element, a reversing switch having two sets of cooperatingmovable contacts directly controlling said motor, driving connectionsbetween one set of contacts and said motor, a pilot motor controlled bysaid controlling element, driving connections between said pilot motorand the other set of contacts. said sets of contacts being successivelyengaeeable to apply successive power impulses to said motor, a secondreversing switch controlling the direction of rotation of said pilotmotor, and operative connections between said controlling element andsaid second reversing switch, whereby the pilot motor is caused to`rotate in a direction corresponding to the direction of movement of saidcontrolling element. a

8. In a system including a controlling element and a controlled elementgoverned thereby, thecombination of a reversible driving motor for saidcontrolled element. a reversing switch having two sets of cooperatingmovable contacts directly controlling said motor, driving connectionsbetween one set of contacts and said motor, a pilot motor controlled bysaid controlling element, driving connections between said pilot motorand the other set of contacts. said sets of contacts being successivelyengageable to anply successive power impulses to said motor, a pair ofneld windings for said pilot motor for effecting reversal in thedirection of rotation thereof, a second reversing switch for selectivelyenergizing said ileld windings, and operative connections between saidcontrolling element and said second reversing switch, whereby the pilotmotor is caused to rotate in a direction corresponding to the directionof movement of said controlling element.

9. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a reversible driving motor for saidcontrolled element, a reversing switch controlling-said motor and havingtwo sets of cooperating movable contacts, driving connections betweenone set of contacts and said motor, a pilot motor controlled by saidcontrolling element, driving connections between said pilot motor andthe 'other set of contacts, said sets of contacts being successivelyengageable to apply successive power impulses to said motor, said oneset oi contacts being mounted in spaced position on a support rotated bysaid corresponding connections, and said other set of contacts beingpositioned between said one set of contacts and movable into variableengagement therewith in accordancewith changes in direction andvariations between the rate of rotation of said motors.

10. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a reversible driving motor for saidcontrolled element, a reversing switch controlling saidmotor and havingtwo sets of cooperating movable contacts, driving connections between none set of contacts and said motor, a pilot motor controlled by saidcontrolling element, driving connections between said pilot motor andsaid other set of contacts, said one set of contacts being mounted inspaced position on a support rotated by said corresponding connections,and

said other set of contacts being positioned bel tween said one set ofcontacts and movable into variable engagement therewith in accordancewith changes in direction and variations between the rate of rotation ofsaid motors, and damping means in the connections between one motor andthe corresponding set of contacts to prevent hunting.

11. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a reversible driving motor for saidcontrolled element, a reversing switch controlling said motor and havingtwo sets of cooperating movable contacts, driving connections betweenone set of contacts and said motor, a pilot motor controlled by saidcontrolling element, driving connections between said pilot motor andsaid other set of contacts, said one set of contacts being mounted inspaced position on a support rotated by said corresponding connections,and

the rate of rotation of said motors, and a dashpot in the connectionsbetween one motor and the corresponding set of contacts to preventhunting.

12. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a reversible driving motor for saidcontrolled element, a reversing switch controlling said motor and havingtwo sets of cooperating movable contacts, driving connections betweenone set of contacts and said motor, a pilot motor controlled by saidcontrolling element, driving connections between said pilot motor andsaid other set of contacts, said one set of contacts comprising twopairs mounted in spaced relation on opposite sides of a center ofrotation by said corresponding operative connections, said other set ofcontacts being positioned between said opposite pairs of contacts' andmounted on opposite sides of said center of rotation by said cororesponding operative connections, said sets of contacts being movableinto engagement in accordance with changes in direction and variationsbetween the rates of rotation of said motors.

13. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a polyphase driving motor for thecontrolled element, a source of polyphase power, a switch having twosets of relatively movable cooperating contacts directly controllingsaid motor, phase connections between one set of said contacts and saidpower source, ldifferent phase connections between the other set of saidcontacts and said power source, operative connections between said motorand one contact of each set of said contacts, and operative connectionsbetween said controlling element and the other contact of each set ofcontacts.

14. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a polyphase driving motor for thecontrolled element, a source of polyphase connections between certain ofsaid contacts of one set and said source for effecting rotation of saidmotor in one direction, phase connections between other` contacts ofsaid one set and said source for effecting rotation of said motor in theopposite direction, and severalr operative connections between saidelements and said two sets of contacts, said sets of contacts beingsuccessively engageable to apply successive power impulses to saidmotor.

15. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a polyphase driving motor for thecontrolled element, a source of polyphase power, a reversing switchinterposed between said motor and source and having two sets ofrelatively movable cooperating contacts, direct phase connectionsbetween certain of said contacts of one set and said source foreffecting rotation of said motor in one direction, phase connectionsbetween other contacts of said one set, and said source for effectingrotation of said motor in the opposite direction. operative connectionsbetween said motor and said one set of contacts. and operativeconnections between said controlling element and said other set ofcontacts, said sets of contacts being successively engageable to applysuccessive power impulses to said motor.

16. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a polyphase driving motor for thecontrolled element, a source of polyphase power, a reversing switchinterposed between said motor and source and having two sets ofrelatively movable cooperating contacts, direct connections betweencertain opposite contacts of one set and certain phases of said motor.means controlled by other contacts of said one set for providing splitphase currentconnections between said means and another phase of saidmotor, operative connections between said motor and one set of contacts,and operative connections between said controlling element and saidother set of contacts.

17. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a polyphase driving motor for thecontrolled element, a source of poli/phase power, a reversing switchinterposed between said motor and source and having two sets ofrelatively movable cooperating contacts, direct connections betweencertain corresponding contacts of one set upon closure and two phases ofsaid. motor. direct Connections between another phase of said motor andthe corresponding phase of said source, means interposed between saidtwo phases of said motor for providing split phase energization thereforupon closure of said certain contacts, operative connections betweensaid motor and one set of contacts, and operative connections betweensaid motor and said other set of contacts.

18. in a system including a controlling element and a controlled elementgoverned thereby, the combination of a three-phase motor for drivingsaid controlled element, a three-phase source, a direct connectionbetween one phase of motor and one phase of said source, a reversingswitch having two sets of cooperating contacts, several connectionsbetween the other two phases oi said motor and the corresponding twophases of said source, one set of said switch contacts being severallyinterposed directly in the lastnamed connections, a condenser interposedbetween the said two phases of said motor for providing split phasecurrent, operative connections between said motor and one set of switchcontacts, and operative connections between said controlling element andthe other set of switch contacts.

lg. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a reversible driving motor for saidcontrolled element, a mechanical diierential interposed between saidmotor and said controliing element, a source of power for said motor, areversing switch interposed between said motor and said source of power,operative connections between the output of said diierential and saidswitch whereby the motor is controlled in accordance with variations inthe degree of movement of said motor and controlling element, anddamping means in said connections.

23. In a system including a controlling element and a controlled eiementgoverned thereby, the combination of driving motor for said controlledelement, a source of power, a switch having two sets oi cooperatingcontacts, connections between one set of said contacts and power sourcefor controlling the initial operation or said motor, connections betweenthe other set of said contacts and said power source for controlling thesubsequent operation of said Inc-tor, operative connections between onecontact of each set of said contacts and said motor, a mechanicalconnection between the other contact of each set oi contacts and saidcontrolling element, whereby the controlling element directly controlssaid switch, and damping means in at least one of said connections.

2l. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a reversible driving motor for saidcontrolled element, a reversing switch h ving two sets of cooperatingcontacts directly controlling said driving motor, a pilot motorcontrolled by said controlling element, mechanical connections betweensaid pilot and driving mo tors and said reversing switch for actuatingthe latter, and damping means at least one of said connections.

22. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a driving motor for said controlledelement, a source of power, a reversing switch having two sets ofcontacts and interposed between said motor and said source, crossconnections between one set of said contacts and the terminals of saidmotor for effecting the reversal thereof upon closure of thecorresponding contacts, operative connections between said motor and oneset of contacts, operative connections between said controlling elementand said other set of contacts, and damping means in one of saidconnections.

23. In a system including a controlling element and a controlled elementgoverned thereby, the combination of a reversible driving motor for saidcontrolled element, a reversing switch controlling said motor and havingtwo sets of cooperating movable contacts, driving connections betweenone set of contacts and said motor, a pilot motor controlled by saidcontrolling element, driving connections between said pilot motor andsaid other set of contacts, a source or power for said pilot motor, asecond reversing switch controlling the direction of rotation thereof,operative connections between said con-a trolling element and saidsecond switch, and

damping means in at least one of said connections.

ARTHUR P. DAVIS. GEORGE AGINS.

REFERENCES ITED The following references are of record in the le of thispatent:

UNITED STATES PATENTS Number Mumber Name Date Trevor Dec. 6, 1927 RabeMar. 8, 1932 Sperry Mar. 22, 1932 Willink Mar. 13, 1934 Moffett Apr. 10,1934 Hodgman Sept. 24, 1935 Potras Dec. 24, 1935 Davis et a1. Feb. 28,1939 FOREIGN PATENTS Country Date France Apr. 8, 1929 Germany Jan. 29,1902

